clutch removal Kelvin J4

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Hello all, I have been enjoying the company of my Kelvin J4 for the best part of a year now, however, last week my prop decided to eat the remains of a duvet and some rope when trying to escape the inevitable grounding out due to lack of water on the K&A... the upshot being that it stopped the engine dead, and, after removing said items, discovered that i had very little forward motionthe clutch would not engage properly and upon inspection of the gearbox that familiar smell of burnt clutchlinings...After hitting the thrust bearing to release the mechanism the chain wheel on the thrust bearing appears to go in quite some distance but fails to engage properly...I would very much like to remove the clutch however every piece of research has only left me more baffled, I have removed the duplex chain and the reversing gear, but roving the clutch appears to be of a different order- I cannot find a step by step guide, and are the lead keys obtainable, and indeed, the key punch( a picture of said article would be helpful!). Any thoughts and advice would be most appreciated, I've just been 'spotted this very morning by the nice chap from CRT, so it looks like I've got 2 weeks either side of Hungerford to complete this mission, I am a sponge here to absorb information, cheers chaps and chapesses!

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Are you VERY sure that there is no debris on the prop shaft immediately in front of the prop? Anything there like wire, rope, plastic bag will stop the clutch engaging forward properly, assuming you have the normal Kelvin gear set up. IIRC on the J, there are opposing steel wedges holding the clutch on, just a case of knocking one of them back to get them out. I would be surprised if you have managed to wear the clutches so much in what sounds like a minor incident.

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Is this the type of gearbox that needs the thrust of the prop in fwd gear to work properly ?

No, as long as the prop and shaft are clear of rubbish, wind the change wheel clockwise and the cone clutch engages, end of.

Please note that Kelvin engines were originally designed for sea going fishing/workboats where reliability was most important- lives depended on the engine getting you home from often dangerous seas. Total gearbox failure or e.g. broken crankshaft would be unheard of. The ability to run on fewer than all cylinders was also a safety feature. The Kelvin designs were approved by Lloyds for sea service and the engines stamped with their inspection number. I doubt you get that with your modern tractor engine conversions.

I think the OP has jumped the gun somewhat- the gearbox won't have failed " just like that".

We shall see......

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ok after first rechecking prop for obstructions decided to have a go..removed starter handle box and chain, duplex reversing gear chain and sprokets/bearings, marked flange to uj joint and any other parts and the phoned Kevin Whittle, and proceeded as per instructions: chocked male part of clutch and supported gearbox on two scissors jacks, undid uj flange, eared lock nut, thrust bearing and control sproket, the 4 bolts connecting g/box to engine, up ended g/box, tapped out thrust bearing whilst supporting end of clutch cones, and here is the resultant evidence, going to take it off to Bristol to get it relined on monday, obvs will inform them the plates sit in an oil bath...

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That ahead clutch doesn't look too bad. The astern one looks nearly new. Someone has machined a key seat in the outer part of shaft- the standard article did not have one.

You need to ensure that when you get it relined the correct IMPERIAL thickness lining is used. ( IIRC this is 5/16 in, but if you need me to I can measure the set of original new linings I have in my spares box) The next nearest size up in metric results in a difference between ahead and astern of about 1/16 of a turn of the gearbox handwheel/clutch thrust box. Finding and holding neutral is nearly impossible if the lining is over thick.

If the lining is the next size down in metric it will start to slip after very little wear- as yours appears to have done.

That lining looks as though it is held on with pop rivets. The originals were tubular rivets. Pop rivets are OK, but they must be the type where the stem comes out as shown . The hard stems, if left in, are likely to wear grooves in the clutch.

Whilst you have the box off check the inside of ahead and astern female clutches for wear and ridging.

The ahead clutch can be removed by undoing the ring nut in the centre (Jam the flywheel and hit the nut with a punch and a big hammer on one of the ears if you don't have a proper spanner). Removing the ring nut will reveal the ends of the four taper keys. Two will be bigger ends and two smaller. Drive the smaller ends forward into the lead stops, which will deform and push the other key out and loosen everything up. Take the keys out then pull the clutch off the crankshaft. Have a good look at the ahead thrust bearing and its white metal seal which are hidden by the clutch.

If there are no lead key stops you are in the poo. You will have to drill and tap the ends of the keys so that you can hold the big end one and drive the little end one in. As the book warns this can be a difficult operation.

To reassemble you need two lumps of lead about 1/4 in square and as long as the ends of a pair of keys. Plumbers solder sticks can be sawn to the right size or it is not hard to melt some lead with a blowlamp on an old spoon and make your own. A well-dried Plaster of Paris mould is fine.

Put the clutch on the crankshaft. Put the lead into the key holes. Put the top keys in - big ends go in first- and then slide the other two keys small end first under them. Tap the lower keys to tighten it all up. The ends of the keys should sit just inside the key groove- they must not project past the end or the rig nut won't hold the clutch on. Refit the crankshaft nut and tighten it the same way you removed it. Get it bloody tight.

Then you can reassemble the box.

N

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Thanks for all that info, have checked the condition of the clutch drums, no scoring or pitting, have seen the bloke at the relining shop, both cones are being replaced as he proposed both rivetting and bonding as a belt and braces approach, after measuing up the metric equivelent worked out at 4.8mm, I suggested possibly taking it up to 5mm however it appears that i would have had problems puttin the bugger in - if you can measure your spare imperial set i would be much obliged- am puttin the process on hold until i have that information, it appears that 4.8mm is larger than 5/16"- he seems to know his onions !

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my new linings ( which have a woven structure) are between 0.218 and 0.205. I think that is 7/32 nominal. In metric 5.5mm.

I would expect that 6 mm would be a bit much but if neccessary a thick gasket on the front of the gearbox would give a bit more room. The standard gasket also seals the ahead thrust bearing so you would need a special for just the g/box casing.

I would expect to need to send the female clutches in as well if the linings are to be bonded.They are usually needed to maintain the pressure on the bond until the glue sets.